1. Field of the Invention
The present invention relates to an image lens system, and more particularly, to a compact image lens system used in electronic products.
2. Description of the Prior Art
In recent years, with the popularity of portable electronic products having photographing function, the demand of compact imaging lens system has grown. Generally, the sensor of a general photographing camera is none other than CCD (Charge Coupled Device) or CMOS device (Complementary Metal Oxide Semiconductor device). Furthermore, advances in semiconductor manufacturing technology have allowed the pixel size of sensors to be reduced and therefore lead compact imaging lens systems to higher resolution. In the meantime, the demand for better image quality is also increased.
A conventional imaging lens system with high imaging power, such as the one set forth in U.S. Pat. No. 7,365,920, generally has a front stop and four lens elements; wherein, the first and second lens elements are adhered together to form a doublet for correcting the chromatic aberration. However, this kind of arrangement has the following disadvantages. First, the degree of freedom in arranging the lens system is curtailed due to the employment of excessive number of spherical glass lenses; thus, the total track length of the system cannot be reduced easily. Second, the process of adhering glass lenses together is complicated, posing difficulties in manufacturing. Moreover, the popularity of high-class portable devices such as Smart Phone and PDA (Personal Digital Assistant) drives the rapid improvements in high resolution and image quality of the current compact imaging lens systems, conventional four lens elements systems no longer satisfy the higher level camera modules. On the other hand, although a five-lens-element image system can provide higher resolution to satisfy the current demand for high-end imaging, a conventional image capturing lens system with five lens elements usually has the disadvantage of excessively long total track length, and thereby is not suitable for compact electronic devices.
Inasmuch as the foregoing, a need is continuously existed for a lens system with good image quality and moderate total track length and is suitable for applying for compact and portable electronic products.